干旱区生态环境知识资源中心(Arid): Incipient Weathering of the similar to 74ka Young Toba Tuff (YTT) Biotite Grains, Sagileru Valley, Andhra Pradesh

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DOI	10.1007/s12594-019-1362-y
	Incipient Weathering of the similar to 74ka Young Toba Tuff (YTT) Biotite Grains, Sagileru Valley, Andhra Pradesh
	Krishnan, Geethanjali; Achyuthan, Hema
通讯作者	Achyuthan, H (corresponding author), Anna Univ, Dept Geol, Chennai 600025, Tamil Nadu, India.
来源期刊	JOURNAL OF THE GEOLOGICAL SOCIETY OF INDIA
ISSN	0016-7622
EISSN	0974-6889
出版年	2019
卷号	94 期号:6 页码:573-578
英文摘要	The Young Toba Tuff (YTT) ash containing biotite flakes was once spread over the Indian peninsula, and is now exposed at several sites in the Sagileru river basin in Andhra Pradesh. The ash beds form a distinct marker horizon in the landscape and have been recognized in a variety of sedimentary sequences associated with middle Paleolithic archaeological tools. In the present study, biotite grains from the volcanic ash beds were separated that were collected from Vankamarri (VKM), Porumamilla (PRM) and Jammulamadugu (JMD), sites in the Sagileru river valley, Cuddapah, Andhra Pradesh. The biotite grains were separated to understand the state and stage of weathering since the ash deposition similar to 74ka. Electron microprobe data of the biotite grains exhibit low FeO/MgO values. The chemical discrimination diagrams characterizing the physicochemical properties of the biotite flakes from VKM, PRM and JMD sites indicate calc-alkaline composition and in the A-CN-K diagram, most of the samples fall above the plagioclase feldspar zone signifying low degree of alteration. Both the CIA and A-CN-K values depict the low weathering state of biotite, and this probably is owing to long periods of dry, semi-arid to arid climatic conditions since similar to 74ka. Scanning Electron microscope (SEM) of the biotite grains reveal micro and nanopores on the surface and many a times these coalesce to form curls along the edges of the biotite grains further supporting incipient but very early stage of biotite weathering since its deposition similar to 74ka.
类型	Article
语种	英语
收录类别	SCI-E
WOS记录号	WOS:000511430800003
WOS关键词	SEDIMENTARY-ROCKS ; INDIAN SUBCONTINENT ; CRUSTAL EVOLUTION ; SOUTHERN INDIA ; GEOCHEMISTRY ; PROVENANCE ; SUMATRA ; BELT ; PETROGENESIS ; MINERALOGY
WOS类目	Geosciences, Multidisciplinary
WOS研究方向	Geology
资源类型	期刊论文
条目标识符	http://119.78.100.177/qdio/handle/2XILL650/369577
作者单位	[Krishnan, Geethanjali; Achyuthan, Hema] Anna Univ, Dept Geol, Chennai 600025, Tamil Nadu, India
推荐引用方式 GB/T 7714	Krishnan, Geethanjali,Achyuthan, Hema. Incipient Weathering of the similar to 74ka Young Toba Tuff (YTT) Biotite Grains, Sagileru Valley, Andhra Pradesh[J],2019,94(6):573-578.
APA	Krishnan, Geethanjali,&Achyuthan, Hema.(2019).Incipient Weathering of the similar to 74ka Young Toba Tuff (YTT) Biotite Grains, Sagileru Valley, Andhra Pradesh.JOURNAL OF THE GEOLOGICAL SOCIETY OF INDIA,94(6),573-578.
MLA	Krishnan, Geethanjali,et al."Incipient Weathering of the similar to 74ka Young Toba Tuff (YTT) Biotite Grains, Sagileru Valley, Andhra Pradesh".JOURNAL OF THE GEOLOGICAL SOCIETY OF INDIA 94.6(2019):573-578.